Portable equipment, e.g. a handheld device or a wearable device such as a breathing mask, can be equipped with or connected to a communication device in order to enable the wearer of the equipment to communicate with other persons. The communication device comprises typically a microphone and an audio amplifier and/or a radio transceiver; additionally the communication device may comprise a display unit. For example, a fire fighter wearing a breathing mask has to be able to communicate with other fire fighters and with fire chiefs and/or images and videos may be broadcasted between communication devices. Typically communication can be voice, data, and/or image/video communication. Additionally, data can be digitally packetized audio, video and/or image. Members of an operational team such as fire fighters constitute an ad-hoc communication group within which all the members have to be able to communicate with all other members of the operational team. The members of the operational team may use, for example, short range radio transceivers for communication within the operational team. Furthermore, a member of an operational team has to be able to communicate with persons outside the operational team. For example, a fire fighter may have a need to communicate with personnel located outside incident or operating area. Generally, the said personnel can be situated so far from the place in which the fire fighters are operating that usually a permanent, not an ad-hoc, communication network is needed for providing communication connections between the fire fighters and the personnel outside incident or operating area. The permanent communication network can be, for example, a mobile communication network or a landline network.
Publication WO2006136992 discloses a method and apparatus for establishing a virtual ad-hoc network. First, under the assistance of a cellular mobile communication network, a plurality of point-to-point enabled communication devices performs multicast connectivity testing. Then, a group of communication devices that can communicate directly with each other are determined from the plurality of the communication devices according to the multicast connectivity testing result and the cellular mobile communication network allocates radio resources to the group of communication devices for performing virtual ad-hoc network communication. Next, the sending orders for each communication device in the group of communication devices are determined on the basis of the principle that only one communication device is allowed to use the radio resources to send data at a time. Finally, the communication devices are arranged to transfer data in the determined sending orders via the point-to-point direct links between them by utilizing the same radio resources. The object of the above-described solution disclosed in WO2006136992 is to implement a system that is able to provide an ad-hoc multicast network for applications similar to real-time communication between multiple persons. There is, however, a need for further development for connecting an ad-hoc communication network to a permanent communication network in a situation in which a communication link between the permanent communication network and the ac-hoc communication network is a half-duplex communication link and the ad-hoc communication network can be either a full-duplex or half-duplex communication network.